Reaktionsprodukte aus 3‐Dimethylamino‐2, 2‐dimethyl‐2H‐azirin und Phthalohydrazid bzw. Maleohydrazid

Reaction Products from 3‐Dimethylamino‐2,2‐dimethyl‐2 H ‐azirine and Phthalohydrazide or Maleohydrazide 3‐Dimethylamino‐2, 2‐dimethyl‐2H‐azirine (1) reacts in dimethylformamide at room temperature with the six‐membered cyclic hydrazides 2, 3‐dihydrophthalazin‐1, 4‐dione (2) and 1, 2‐dihydropyridazin‐3, 6‐dione (15) to give the zwitterionic compounds 3 and 16 , respectively ( Scheme 1 and 7 ). The mechanism of these reactions is outlined in Scheme 1 for compound 3 ( cf. also Scheme 8 ). The first steps are thought to be similar to the known reactions of 1 with the NH‐acidic compounds saccharin and phthalimide ( cf. [1]). Instead of ring expansion to the nine‐membered heterocycle i (X=CONH, Scheme 8), a proton transfer followed by the loss of water gives 3 ( Scheme 1 ). The structure of the zwitterionic compounds 3 and 16 is deduced from spectral data and the reactions of these compounds (see Schemes 2, 3, 4, 6 and 7 ). Methylation of 3 yields the iodide 4 , which is hydrolysed easily to the 2‐imidazolin‐5‐one derivative 5 ( Scheme 2 ). Hydrolysis of 3 under basic conditions leads to the amide 6 , which undergoes cyclization to 7 at 220–230° ( Scheme 3 ). The analogous cyclization has been realized under acidic conditions in the case of 17 ( Scheme 7 ). Catalytic reduction of 3 yields the tertiary amine 14 ( Scheme 6 ), whereas the reduction with sodium borohydride leads to a mixture of 14 and the 2‐imidazoline derivative 13 . The alcohol 11 , corresponding to the amine 14 , is obtained by sodium borohydride reduction of the 2‐imidazolin‐5‐one 7 or of the amide 6 ( Scheme 3 ). This remarkably easy reaction of 7 shows the unusual electrophilicity of the lactamcarbonyl group in this compound. The reduction of 6 to 11 is understandable only by neighbouring group participation of N (2′) in the dihydrophthalazine residue.